util/ralloc: add memdup

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27762>

src/util/ralloc.h

@@ -313,6 +313,11 @@ void *ralloc_parent(const void *ptr);
  */
 void ralloc_set_destructor(const void *ptr, void(*destructor)(void *));
 
+/**
+ * Duplicate memory, allocating the memory from the given context.
+ */
+void *ralloc_memdup(const void *ctx, const void *mem, size_t n) MALLOCLIKE;
+
 /// \defgroup array String Functions @{
 /**
  * Duplicate a string, allocating the memory from the given context.